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No Heat From Heater


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Hi all I have no heat at all from my heating system and with winter approaching I think I had better look at this sooner rather than later. The car warms up ok and the blower fans are working fine.

The car was standing for about 10 years before I bought it, so I am wondering if the matrix is sludged up.

Does anybody have a check list of things I can go through to identify the problem before I start taking things apart as I understand getting to the matrix is a bit of a task?

Thanks

Rob

Edited by robington
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Easiest thing to try is to backflush the heater matrix. The flow goes from the pipe exiting the cylinder head at the rear, this pipe runs under the plenum. Undo the hose to the head from this pipe and fit a suitable length of hose to direct the effluvium somewhere safe...(!).... then you have to undo and remove the heater hose where it runs into the water pump. Get your garden hose and a suitable joining piece (13mm copper tube or similar works well) and connect it to the water pump hose you have just removed. Make sure the heater is "ON"....

Turn on the water tap to the garden hose. Carefully........this will backflush the heater matrix and the stuff that comes out of the other end will both astonish and disgust you!! Be careful where the muck goes, as it is liable to come out at some pressure...and hence flow rate...and can be Very Messy Indeed. This procedure worked on mine, and the heater became functional once more. The idea of having to remove the matrix fills me with dread.

Scientists investigate that which already is; Engineers create that which has never been." - Albert Einstein

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It's also worth checking that the air flow direction flaps are operating correctly.

If you search the forum you'll find loads of post on the subject & how to fix the problem.

Cheers,

John W

http://jonwatkins.co.uk

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Had the same problem when I bought mine, no heat from the vents at all. Took it into The Lotus Service Centre as had no idea of where to start looking. When I collected it, they said it was a faulty one way valve that was loacated somewhere in the engine compartment but I cant remember where! They did give me the old valve which from memory was brass and about 2 inches long.

Looked at my service history and found the receipt but all it says is "replaced faulty one way valve".

So I guess that this valve must be in-line in a hose somewhere?

Edited by esprit22
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Interesting topic as neither of the heaters work in my turbo Esprits so I shall have a look at your suggestions when I next feel like getting my hands dirty.

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The non-return valve is in the vacuum takeoff line from the vacuum rail that joins the individual inlet manifold throats. The vacuum is used to operate the air flaps that allow air directly into the cabin and/or through the heater matrix. There's a vacuum reservoir under the RH engine side trim panel, just below the RH side quarter window.

Scientists investigate that which already is; Engineers create that which has never been." - Albert Einstein

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Rob,

Ensure that the coolant/rad etc is purged of air. I had to undo the vent on top of the radiator and purge some trapped air in order to get my heater working. Access to the vent is via a half-round plastic cover that is nestled next to the light motor on the left side.

Dan

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  • 2 weeks later...

ive just tried to get heat out of mine!!! - Nothing.

now i suspect its something else in my case - when i try to push the heater slider thing to the left (towards heater/vent/off position)

it will go no further than Heater, if i push, it just slides back!

i suspect a stuck valve or something but i have no idea how the system works...

_DSC2905.JPG

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"Whats this supposed to do anyway????!!!!" is the dimmer switch for the dashboard. Mine wasn't connected up when I got my car and didn't do anything, so if yours is the same thats why you may find it to be a useless knob!

Regarding your heater switch, these connect to flaps on the heater assembly burried deep under the dash (hence why the job of replacing the matrix itsellf fills everyone with dread - have done it, and they are right). May be worth checking the cables connecting the switch to the flaps are present and working (again, were missing in my car and moving the controls did nothing).

It took me ages to get my head around how the heating system works, but as others have said put half an hour aside and som some searching, there are plenty of threads and some write ups too.

Edited by Nelly9000
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  • 3 weeks later...

Thanks Neil.

Ah right, yes that would make sense, however why is there a dimmer knob AND a dimmer switch on the other side??!! damn lotus being cryptic.....

Well i had a poke about under the dash last night (my neck is still stiff this morning!)

OK - the heater pipes are warm, both of them, which is good.

on moving the "Flap control" slider, i can clearly see it acting on the cam connected via a rod to a rotating input to the top-right side of the heater box. seems all to be moving ok. If i push the slider over fast, it gets to "heater" and i can hear a loud clunk from the heater box, presumably a flap hitting home.

however no heat....

What is the construction inside the heater box like???

I see there is a vacuum line attached to the slider-cam device - whats this for? note - the flap under the cover in the front bonnet does not move. (although it can be moved by hand.

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I see there is a vacuum line attached to the slider-cam device - whats this for?

It's the vacuum that actually provides the power to operate the flaps.

Cheers,

John W

http://jonwatkins.co.uk

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I thought it may... its VERY had to see what's going on under there....

So the flaps inside the heater box are vacuum controlled too? whats the rotating input do then?

any chance of whipping up a little diagram of the general system and whats inside the box? pleeeeeeeese?! :-)

i wonder if i have a vacuum leak... there is an annoying ticking from the brake master cylinder after the brake is depressed...

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Only thing I can think of is that the matrix itself has had it. I had mine recorred and at the time it was something like 90% restricted - so buggered, basically.

It is essentially a small radiator unit - although the two pipes may be warm, I would think that may not mean the matrix itself is working as thats what actually supplies the heat.

Oh - one thought I have just had, there are two flaps in the assembly. You have confirmed one is working as you can hear it clunk - is the other working? That may wll be why your lever does not go all the way to the right if its actually seized inside the assembly. You can access both the levers on the side of the assembly from the drivers footwell - one is at the top of the assembly and one at the bottom.

Good luck!

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i wonder if i have a vacuum leak.

The most likely problem is one of the thin, black plastic tubes has come adrift from one of the rubber elbows/T-pieces.

The vacuum is taken off the inlet manifold & stored in a tank which sits above the left hand fuel tank & then is taken to the heater via a thin, black plastic tube through the buttress & down the left hand windscreen pillar.

any chance of whipping up a little diagram of the general system and whats inside the box? pleeeeeeeese?! :-)

Not from memory, but the whole system is described & shown in full detail in the workshop manual. If you don't have one perhaps someone could upload the relevant pages for you, I'm not a full member so I can't.

As I said in an earlier post "If you search the forum you'll find loads of post on the subject & how to fix the problem."

Cheers,

John W

http://jonwatkins.co.uk

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Easiest thing to try is to backflush the heater matrix. The flow goes from the pipe exiting the cylinder head at the rear, this pipe runs under the plenum. Undo the hose to the head from this pipe and fit a suitable length of hose to direct the effluvium somewhere safe...(!).... then you have to undo and remove the heater hose where it runs into the water pump. Get your garden hose and a suitable joining piece (13mm copper tube or similar works well) and connect it to the water pump hose you have just removed. Make sure the heater is "ON"....

Turn on the water tap to the garden hose. Carefully........this will backflush the heater matrix and the stuff that comes out of the other end will both astonish and disgust you!! Be careful where the muck goes, as it is liable to come out at some pressure...and hence flow rate...and can be Very Messy Indeed. This procedure worked on mine, and the heater became functional once more. The idea of having to remove the matrix fills me with dread.

I am going to have a go at this over the weekend. Any chance of an engine bay photo pointing out the location of the heater matrix hoses?

Thanks

Rob.

Edited by robington
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One hose fits to the water pump itself, at the front of the engine concealed by the cambelt. You have to flush FROM this one, TO the hose that fits to the pipe running to the back of the cylinder head...runs under the plenum chamber in a metal pipe..you can disconnect the hose from the front of the pipe or the rear of the pipe from the head. Probably easiest to disconnect the metal pipe from the head and then put a length of garden hose on the metal pipe, so you can direct the output of your flushing activity somewhere more sensible than into your face or the washing machine....(!) Connect the waterpump end hose to the mains water supply with a garden hose and a suitable joiner, then turn the heater ON followed by the water supply....increase the flow slowly until a great dollop of filth comes flying out into your bucket...ah...didn't mention the bucket (!)...a good idea to direct the output into a bucket! Sorry...can't do photos, no camera at present.

Scientists investigate that which already is; Engineers create that which has never been." - Albert Einstein

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Thank's John

It's the water pump hose that's confusing me, as the only hose I remember going into the water pump is the main hose 28mm dia I think, but I was not looking for the heater hoses then, so I will have a better look if I can get in there!

Rob.

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If I may suggest, do it from the front of the car.

You just have to disconnect the 2 2cm hoses were they come out of the frame in front.

They are connected to two pipes that are side by side just over the anti-roll bar in the middle of the car.

You must flush the hose side (each one), the aluminum pipes are going to the back.

Mine was plugged and leaking, just make sure you don't pressurize things too much, you don't want ending changing the core...

Luc

Something I learned about cars or planes, it all works until it doesn't anymore...sometime there is no way around it!

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FIXED!

Turns out the one way valve between the induction manifold and the vacuum res was faulty, letting to vacuum through.

Luckily i have a spare (but different) one in the garage new from another project. after a bit of fiddling with vacuum lines - HEAT WOO!

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FIXED!

Turns out the one way valve between the induction manifold and the vacuum res was faulty, letting to vacuum through.

Luckily i have a spare (but different) one in the garage new from another project. after a bit of fiddling with vacuum lines - HEAT WOO!

:thumbsup:

Hope I will be joining you with heat soon.

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  • 1 month later...
  • Gold FFM

Vacuum reservoir is on top of fuel tank shaped a mushroom. But not sure whether non turbos have this. I think turbo needs it due to more complex vacuum system.

Vacuum reservoir is on top of fuel tank shaped a mushroom. But not sure whether non turbos have this. I think turbo needs it due to more complex vacuum system.

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The non-return valve is an inline brass thingy in the vacuum line...on mine it's where the line passes the head; one hose clip each side of it.

Scientists investigate that which already is; Engineers create that which has never been." - Albert Einstein

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